Catalysts having metal nano-particle catalyst supported on surface-treated natural cellulose fibers and preparation method thereof

ABSTRACT

The present disclosure relates to a catalyst having metal catalyst nanoparticles supported on natural cellulose fibers and a method of preparing the same, whereby natural cellulose fibers are subjected to specific pretreatment to increase a surface area and form defects on the surface thereof and metal catalyst nanoparticles are then supported on the cellulose catalyst support in a highly dispersed state, thereby providing improved catalysis while allowing production of the catalyst at low cost. The catalyst may be utilized for various catalytic reactions.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a divisional of U.S. application Ser. No. 12/943,547filed Nov. 10, 2010, and claims the benefit of Korean Patent ApplicationNo. 10-2009-0107802, filed with the Korean Intellectual Property Officeon Nov. 10, 2009, the disclosures of which are incorporated herein byreference in their entireties.

BACKGROUND

1. Technical Field

The present disclosure relates to a catalyst having metal catalystnanoparticles supported on natural cellulose fibers and a method ofpreparing the same, whereby natural cellulose fibers are subjected tospecific pretreatment to increase a surface area and form defects on thesurface thereof and metal catalyst nanoparticles are then supported onthe natural cellulose fibers in a highly dispersed state, therebyproviding improved catalysis while allowing production of the catalystat low cost.

2. Description of the Related Art

In the field of catalysts, two major issues have been actively studiedin recent years. One is to prepare a support having a large surface areaand a uniform pore distribution adequate for a corresponding reactionwhile guaranteeing physical and chemical stability and the other is toprepare a catalyst exhibiting maximum activity at minimum cost bysupporting catalyst nanoparticles in a highly dispersed state. Thepresent disclosure relates to preparing a catalyst support having goodporosity and a large surface area from a biomaterial while allowing easysupport of nanocatalyst.

Various methods of processing various biomaterials into carbon materialsthrough pretreatment have been proposed. O. Ioannidou et al. (Renewableand Sustainable Energy Reviews 11 (2007) 1966-2005) disclose a procedurefor processing various agricultural residues into activated carbon.Applicable agricultural residues include wheat, corn straw, olive pits,bagasse, birch wood, miscanthus, sunflower shells, pine cones, rapeseed,cotton residues, olive residues, Eucalyptus maculata, sugar canebagasse, almond shells, peach pits, grape seeds, straw, oat husks, cornstover, apricot pits, cotton stalks, cherry pits, peanut shells, nutshells, rice husks, corncobs, corn husks, hazelnut shells, pecan shells,rice husks, rice straw, etc., which are activated and processed intomaterials with a surface area of hundreds to thousands of m²/g. Itshould be noted that, since the raw materials have significantly varyingcharacteristics, different materials are used for different purposes. Itis also disclosed that materials containing more lignin tend to havemore macropores after activation and those containing more fibers(cellulose) tend to have more micropores following activation.

Fibrous biomaterials like henequen fibers are suitable for use as acatalyst support having physical/chemical durability because of theircharacteristic fiber bundle structure. Since henequen contains a lot ofcellulose components, however, it yields a lot of micropores. Thus,special surface treatment is required to provide more mesopores than themicropores for application to catalytic reactions.

The inventors of the present disclosure carried out research to processfibrous biomaterials such as henequen having a lot of micropores due torich cellulose components into physically/chemically durable catalystsupports, in particular, those appropriate for catalytic reaction. As aresult, we found out that, through a series of electron beam treatment,heat treatment at high temperature and chemical surface treatment usinghenequen fibers as a raw material, a cellulose catalyst support could beprepared which has a large surface area and uniform pore distributionand allows easy support of metal catalyst in a highly dispersed statethrough introduction of functional groups to the surface thereof.

SUMMARY

One aspect of the present disclosure is to provide a catalyst havingmetal catalyst nanoparticles supported on natural cellulose fibers and amethod of preparing the same, in which the metal catalyst nanoparticlesare supported in a highly dispersed state on the natural cellulosefibers having a large surface area and uniform pore distribution, withfunctional groups introduced to the surface of the natural cellulosefibers through specific pretreatment of the natural cellulose fibers,thereby guaranteeing broad applicability to various catalytic reactions.

In accordance with one aspect, a method of preparing a catalyst havingmetal catalyst nanoparticles supported on natural cellulose fibersincludes: treating natural cellulose fibers with an electron beam;heat-treating the electron beam-treated natural cellulose fibers;chemically treating the heat-treated natural cellulose fibers with anacidic solution to introduce an oxidizing group to a surface of thenatural cellulose fibers to prepare a cellulose catalyst support; andsupporting metal catalyst nanoparticles on the cellulose catalystsupport by chemical vapor deposition or impregnation.

In accordance with another aspect, a catalyst having metal catalystnanoparticles supported on natural cellulose fibers includes: acellulose catalyst support pretreated to allow metal catalystnanoparticles to be supported on a surface of natural cellulose fibers;and the metal catalyst nanoparticles supported on the cellulose catalystsupport by chemical vapor deposition or impregnation.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present disclosure will becomeapparent from the detailed description of the following embodiments inconjunction with the accompanying drawings:

FIG. 1 is a scanning electron microscopic (SEM) image of the surface ofa henequen fiber sample depending on electron beam intensity in Example1;

FIG. 2 is an SEM image of the surface of henequen fibers after electronbeam treatment at 10 kGy in Example 1;

FIG. 3 is an SEM image of the surface of henequen fibers after electronbeam treatment at 100 kGy in Example 1;

FIG. 4 is an SEM image of the surface of henequen fibers after electronbeam treatment at 150 kGy in Example 1;

FIG. 5 is an SEM image of the surface of henequen fibers after electronbeam treatment at 200 kGy in Example 1;

FIG. 6 is an SEM image of the surface of henequen fibers after electronbeam treatment at 500 kGy in Example 1;

FIG. 7 is an SEM image of the surface of henequen fibers after heattreatment at 500° C. following electron beam treatment;

FIG. 8 is an SEM image of the surface of henequen fibers after heattreatment at 700° C. following electron beam treatment;

FIG. 9 is an SEM image of the surface of henequen fibers after heattreatment at 1000° C. following electron beam treatment;

FIG. 10 is an SEM image of the surface of henequen fibers after heattreatment at 1500° C. following electron beam treatment;

FIG. 11 shows results of analysis of functional groups introduced to thesurface of henequen fibers after electron beam treatment, heat treatmentand chemical treatment using X-ray photoelectron spectroscopy (XPS);

FIG. 12 is an SEM image of a nickel (Ni) catalyst supported onchemically treated henequen fibers by impregnation in Example 2;

FIG. 13 is an SEM image of a Ni catalyst supported on non-chemicallytreated henequen fibers by impregnation in Example 2; and

FIG. 14 shows results of performing pyrolysis of acetylene (C₂H₂) usinga Ni catalyst supported on a cellulose catalyst support in Example 1 anda Ni catalyst supported on alumina in Comparative Example 1,respectively.

DETAILED DESCRIPTION

Exemplary embodiments of the present disclosure will now be described indetail with reference to the accompanying drawings.

One aspect of the present disclosure provides a method of preparing acatalyst having metal catalyst nanoparticles supported on naturalcellulose fibers. The method includes: treating natural cellulose fiberswith an electron beam (Process 1); heat-treating the electronbeam-treated natural cellulose fibers (Process 2); chemically treatingthe heat-treated natural cellulose fibers with an acidic solution tointroduce an oxidizing group to a surface of the natural cellulosefibers to prepare a cellulose catalyst support (Process 3); andsupporting metal catalyst nanoparticles on the cellulose catalystsupport by chemical vapor deposition or impregnation (Process 4).

The method of preparing a catalyst having metal catalyst nanoparticlessupported on natural cellulose fibers will now be described in moredetail.

Process 1 is a process of treating natural cellulose fibers with anelectron beam to remove impurities oxidized at low temperature from thenatural cellulose fibers.

According to the present disclosure, henequen fibers may be used as thenatural cellulose fibers.

In one embodiment, electron beam treatment is performed by placinguntreated henequen fibers in a polyethylene bag and irradiating anelectron beam of 10-500 kGy to the henequen fibers from an electron gun.The electron gun may have a maximum acceleration energy of 1.0 MeV.During irradiation of the electron beam, an inlet of the plastic bag maybe slightly opened to remove water and ozone produced during electronbeam irradiation, thereby minimizing effects of water and ozone on thehenequen fibers.

Process 2 is a process of heat-treating the electron beam-treatednatural cellulose fibers to remove impurities from the natural cellulosefibers while improving surface area and porosity thereof.

In one embodiment, the electron beam-treated natural cellulose fibersare separated into thin fibers of tens to hundreds of pm and then cutinto short fibers of 1 to 2 mm in length, with the natural cellulosefibers submerged in liquid nitrogen.

Then, the cut natural cellulose fibers are heated from 500 to 1500° C.at a rate of 5 to 20° C./min under in an atmosphere composed of a 1:1mixture of hydrogen and nitrogen. Subsequently, the temperature ismaintained at 500 to 1500° C. for 0.5 to 2 hours to carbonize thenatural cellulose fibers. Alternatively, the temperature may bemaintained in the range of 500 to 1000° C. for 0.5 to 2 hours.Advantageously, the temperature may be maintained at 700° C. for 0.5 to2 hours. During this process, impurities are removed from the naturalcellulose fibers, so that the thickness of the natural cellulose fibersmay be decreased and the spaces previously occupied by the impurities(such as wax or fat components) may remain as pores.

Process 3 is a process of chemically treating the heat-treated henequenfibers with an acidic solution for introduction of an oxidizing group tothe surface of the natural cellulose fibers to prepare a cellulosecatalyst support. More specifically, in Process 3, the heat-treatednatural cellulose fibers may be subjected to chemical treatment with theacidic solution for introduction of the oxidizing group such as CO—,CH—, O—C═O, CO₂, or CO₃ to the surface of the natural cellulose fibersto prepare the cellulose catalyst support.

In one embodiment, in the process of chemically treating theheat-treated natural cellulose fibers, the heat-treated naturalcellulose fibers are immersed in 0.1˜0.5 mol sulfuric acid aqueoussolution and then subjected to sweeping in 10˜60 cycles at −0.15˜1.3 Vat a sweep rate of 50 mV/s. Then, the natural cellulose fibers may beimmersed in a 30% nitric acid solution (or 14N nitric acid solution) andchemically treated at 10˜150° C. for 10˜20 minutes under reflux.Alternatively, the natural cellulose fibers may be immersed in a mixturesolution of nitric acid (14M, 50 mL) and sulfuric acid (98%, 50 mL) orin a solution of 98% sulfuric acid and 70% nitric acid in a volume ratioof 3:1 and treated at 50˜70° C. for 5 minutes to 6 hours under reflux.After sufficiently washing the chemically treated natural cellulosefibers with distilled water and filtering, the natural cellulose fibersare dried at 110° C. for 12 hours, thereby providing a cellulosecatalyst support.

Process 4 is a process of supporting metal catalyst nanoparticles on thecellulose catalyst support by chemical vapor deposition or impregnation.

Examples of the metal catalyst nanoparticles to be supported on theprepared cellulose catalyst support include, but are not limited to,platinum nanoparticles, nickel nanoparticles, cobalt nanoparticles, andmolybdenum nanoparticles. To allow the metal catalyst nanoparticles suchas platinum nanoparticles, nickel nanoparticles, cobalt nanoparticles ormolybdenum nanoparticles to be supported on the cellulose catalystsupport, chemical vapor deposition or impregnation may be used.

In one embodiment, the process of supporting the metal catalystnanoparticles on the cellulose catalyst support by chemical vapordeposition may be carried out as follows. First, the cellulose catalystsupport subjected to pretreatment of Processes 1 to 3 are placed at thecenter of a quartz tube in the middle of a furnace, and impurities areremoved from the quartz tube by maintaining the quartz tube at apressure of 6˜10 Torr at 110˜120° C. for 30˜120 minutes. Then, anitrogen flow (50˜300 sccm) is supplied thereto for over 1 hour. In thisprocess, the internal temperature of the quartz tube is elevated to80˜300° C. at a rate of 10° C./minute and a vapor metal precursor flowis initiated once the reaction temperature is reached, so that the metalcatalyst nanoparticles can be supported on the cellulose catalystsupport. The metal precursor is injected in advance into a vaporatordisposed in a heating oven. For example, in the case of using a platinumprecursor (MeCpPtMe₃) as the metal precursor, the platinum precursor isheated to 60˜80 ° C. and a stopcock of a connection tube is opened oncethe reaction temperature is reached, so that the gaseous metal precursorcan be conveyed to the cellulose catalyst support within the reactor.The cellulose catalyst support is maintained at a reaction temperatureof 80˜300° C. for 30 minutes to 24 hours, and the amount of metalcatalyst nanoparticles supported on the cellulose catalyst supportincreases with increasing reaction time. As the platinum precursor,Pt(Me)₃(Cp), Pt(Tfacac)₂, Pt(Me)(CO)(Cp), Pt(Me)₂(COD),[PtMe₃(acac)]₂(acac; acetylacetonato ligand), PtCl₂(CO)₂, Pt(PF₃)₄,Pt(acac)₂, or Pt(C₂H₄)₃ may also be used. Examples of the nickelprecursor include, but are not limited to, nickel nitrate (Ni(NO₃)₂) andnickel tetracarbonyl (Ni(CO)₄). Examples of the cobalt precursorinclude, but are not limited to, Co(CO)₃NO and Co(NO₃)₂, and an exampleof the molybdenum precursor includes Mo(CO)₆. In this process, chemicalvapor deposition provides an advantage of effectively increasing theamount of metal catalyst nanoparticles supported on the cellulosecatalyst support without increasing the size of the metal catalystnanoparticles or decreasing the degree of dispersion thereof even in thecase of increased reaction time. In another embodiment, the process ofsupporting the metal catalyst nanoparticles on the cellulose catalystsupport by impregnation may be carried out as follows. First, any of theaforementioned metal precursors may be used to support the metalcatalyst nanoparticles on the cellulose catalyst support after obtainingthe metal catalyst nanoparticles through pretreatment of Processes 1 to3. The pretreated cellulose catalyst support is deposited in an aqueoussolution (0.1˜1 mol) of a metal precursor, subjected to ultrasonicationfor 5 minutes to 3 hours, and remains in the solution for 12 hours. Theresulting cellulose catalyst support in a slurry state is filtered fromthe solution, dried in an oven at 100-120° C. for over 12 hours, andburnt in a furnace of 400 to 600° C. for 2˜6 hours under nitrogenatmosphere. As a result, a catalyst having the metal catalystnanoparticles supported on the cellulose catalyst support may beobtained.

Another aspect of the present disclosure provides a catalyst havingmetal catalyst nanoparticles supported on natural cellulose fibers. Thecatalyst includes: a cellulose catalyst support pretreated to allowmetal catalyst nanoparticles to be supported on a surface of naturalcellulose fibers; and the metal catalyst nanoparticles supported on thecellulose catalyst support by chemical vapor deposition or impregnation.

The cellulose catalyst support pretreated to allow the metal catalystnanoparticles to be supported on the surface of the natural cellulosefibers may be prepared by treating natural cellulose fibers with anelectron beam; heat-treating the electron beam-treated natural cellulosefibers; and chemically treating the heat-treated natural cellulosefibers with an acidic solution to introduce an oxidizing group to thesurface of the natural cellulose fibers.

The pretreatment for preparing the cellulose catalyst support isperformed under the same conditions as the pretreatment of Processes 1to 3 described above in the method of preparing the catalyst havingmetal catalyst nanoparticles supported on the natural cellulose fibers.

The catalyst having platinum catalyst nanoparticles supported on thecellulose catalyst support is suitable for hydrogenation of tetralin orbenzene, oxidation of methanol, ethanol or phenol, and the like.

The catalyst having nickel catalyst nanoparticles or molybdenum nickelcatalyst nanoparticles supported on the cellulose catalyst support iswell suited for desulfurization, denitrification, demetallation, and thelike.

The catalyst having cobalt catalyst nanoparticles supported on thecellulose catalyst support may be used as a co-catalyst fordesulfurization, denitrification, or demetallation. Specifically, thecatalyst having the cobalt catalyst nanoparticles supported on thecellulose catalyst support may be used as a co-catalyst for platinumcatalysts in fuel cells, catalysts for Fisher-Tropsch reaction,catalysts for oxidation and partial oxidation of hydrocarbons, catalystsfor reforming reactions, catalysts for amination of ethanol or the like,catalysts for hydrogenation, catalysts for water-gas shift reactions,and the like.

Next, the present disclosure will be described with reference toexamples. It should be understood that the present disclosure is notlimited to the following examples and may be embodied in different ways,and that these examples are given to provide complete disclosure of theinvention and to provide thorough understanding of the presentdisclosure to those skilled in the art. The scope of the presentdisclosure is limited only by the accompanying claims and equivalentsthereof.

EXAMPLES Example 1 Preparation of Cellulose Catalyst Support UsingHenequen Fibers and Preparation of Nickel (Ni) Nanocatalyst Using theSame as Catalyst Support

(1) Electron Beam Treatment for Removing Impurities from Henequen Fiber

Henequen fibers were subjected to electron beam treatment to removeimpurities oxidized at low temperature therefrom. For electron beamtreatment, untreated henequen fibers were placed in a polyethylene bagand an electron beam of 10 to 500 kGy was irradiated thereto from anelectron accelerator (ELV-4 type, EB Tech Co., Ltd.). During electronbeam irradiation, the inlet of the plastic bag was slightly opened toremove water and ozone produced during the electron beam irradiation tominimize the effects thereof on the henequen fibers. The maximumacceleration energy of the electron gun was 1.0 MeV. The electron beamirradiation was carried out in air while moving the sample at a constantspeed of 10 m/min on a conveyor belt with the current set at 4.95 mA.

(2) Heat Treatment of Electron Beam-Treated Henequen Fibers for Removalof Impurities and Improvement of Surface Area and Porosity

The electron beam-treated henequen fibers were heat-treated underspecific heat treatment conditions to remove impurities and improvesurface area and porosity. The electron beam-treated henequen fiberswere separated into thin fibers of tens to hundreds of pm and then cutinto short fibers of 1 to 2 mm in length after impregnating the fibersin liquid nitrogen. The cut henequen fibers were heated to 500˜1500° C.at a rate of 5˜20° C./min under an atmosphere of a 1:1 mixture ofhydrogen and nitrogen. Then, the temperature was maintained at 500 to1500° C. for 1 hour to carbonize the henequen fibers.

(3) Chemical Treatment of Heat-Treated Henequen Fibers for Introductionof Functional Groups to Allow Easy Support of Metal CatalystNanoparticles

The heat-treated henequen fibers were immersed in 0.5M aqueous sulfuricacid solution and subjected to sweeping in 10 to 60 cycles from −0.15 to1.3 V at a sweep rate of 50 mV/s. The henequen fibers were immersed in amixture of nitric acid (14M, 50 mL) and sulfuric acid (98%, 50 mL) andthen chemically treated at 60° C. for 10 minutes under reflux. Aftersufficiently washing the sample with distilled water and filtering, thetreated sample was dried at 110° C. for 12 hours. As a result, acellulose catalyst support was prepared.

(4) Supporting of Metal Catalyst Nanoparticles on Cellulose CatalystSupport by Chemical Vapor Deposition

To support the Ni nanocatalyst on the surface of the resulting cellulosecatalyst support by chemical vapor deposition, the obtained cellulosecatalyst support was placed in a quartz tube positioned in the middle ofa furnace. After maintaining the tube at a pressure of 6 Torr at 110° C.for 30 minutes to remove impurities from the inside of the quartz tube,nitrogen (100 sccm) was supplied thereto for over 1 hour. Then, afteradding Ni(CO)₄ to a vaporizer, N₂ was supplied while keeping thetemperature at 35° C., so that the gaseous nickel precursor (Ni(CO)₄)could be conveyed to the cellulose catalyst support in the reactor. As aresult, a catalyst having Ni nanoparticles supported on the cellulosecatalyst support was obtained. It was observed that the amount of the Ninanoparticles supported on the cellulose catalyst support increased withreaction time.

Example 2 Preparation of Cellulose Catalyst Support Using HenequenFibers and Preparation of Ni Nanocatalyst Using the Same as CatalystSupport

A Ni nanocatalyst was prepared in the same manner as Example 1, exceptthat Ni nanoparticles were supported on the cellulose catalyst supportby impregnation.

The pretreated cellulose catalyst support was deposited in an aqueoussolution (1M) of a metal precursor Ni(CO)₄. After ultrasonication for 1hour, the catalyst support was allowed to stand in solution for 12hours. The resulting cellulose catalyst support in slurry state wasfiltered from the solution, dried in an oven at 100 to 120° C. for over12 hours, followed by burning in a furnace at 400 to 600° C. for 3 hoursunder nitrogen atmosphere. As a result, a catalyst having Ninanoparticles supported on the cellulose catalyst support was obtained.

COMPARATIVE EXAMPLE Comparative Example 1 Preparation of Ni CatalystSupported on Alumina by Initial Impregnation Using CommerciallyAvailable γ-Alumina as Catalyst Support

(1) Supporting of Ni Precursor on γ-alumina by Initial Impregnation

γ-Alumina (γ-Al₂O₃, 97%, Strem) was used as a support, and a 1M aqueousprecursor solution was prepared by dissolving nickel nitrate (Ni(NO₃)₂)as a Ni precursor in distilled water. Then, after drying the alumina inan oven of 110° C. for over 12 hours, a Ni catalyst supported on aluminawas prepared by initial impregnation.

(2) Preparation of Metal Oxide Catalyst Through Drying and Burning

The Ni precursor-supported catalyst prepared by initial impregnation wasdried in an oven at 110° C. for over 12 hours and treated in a furnaceat 450° C. for 4 hours under nitrogen atmosphere. As a result, a nickeloxide catalyst supported on alumina was obtained.

TEST EXAMPLE Test Example 1 Change in Surface Shape of Henequen FibersDepending on Electron Beam Intensity

The change in the surface shape of the henequen fibers treated withelectron beams (electron beam intensity=10˜500 KGy) in Process 1 ofExample 1 was observed by scanning electron microscopy (SEM). Resultsare shown in FIGS. 1 to 6.

As shown in FIG. 1, the original henequen fiber sample had pores with aninner channel size of about 2˜5 μm. As seen in FIGS. 2 to 6, the innerchannels increased to a diameter of approximately 10 μm whilemaintaining a relatively uniform shape.

Test Example 2 Change in Surface Area Depending on Heat Treatment ofHenequen Fiber

In Process 2 of Example 1, the electron beam-treated henequen fibers(treated at 10 kGy and 100 kGy) were subjected to heat treatment undervarious conditions. BET surface area measurement was performed andresults are shown in Table 1. The heat treatment was carried out whilesupplying a mixture of hydrogen and nitrogen having a volume ratio of1:1. The heat treatment temperature was varied from 500 to 1500° C.

TABLE 1 BET surface area (m2/g) Heat treatment Henequen fibers (10Henequen fibers (100 temperature (° C.)^(a) kGy) kGy) Beforeb 6 5 500230 263 700 355 360 800 372 374 1000 380 383 1200 122 121 1500 50 50^(a)Heat-treated for 1 hour under nitrogen and hydrogen atmospherebBefore heat treatment

As can be seen from Table 1, the henequen fibers treated only withelectron beams had a small surface area of 5 or 6 m²/g. Upon heattreatment at 500° C., the surface area of the henequen fibers increasedconsiderably to 230 or 263 m²/g. This is because the impurities inchannels and pores were removed by the heat treatment and only stablecomponents at high temperature remained. The surface area of thehenequen fibers increased with the heat treatment temperature. However,above 1000° C., the surface area decreased abruptly. This is because thecomponents constituting the inner structure of the henequen fibers arepartially decomposed at high temperature. For this reason, the henequenfibers treated at 1500° C. had a surface area of only about 50 m²/g.

Test Example 3 Change in Shape of Henequen Fibers Depending on HeatTreatment Conditions

SEM analysis was performed on the henequen fibers treated in Processes 1and 2 of Example 1. The results are shown in FIGS. 7 to 10.

FIG. 7 is an SEM image of the henequen fibers heat-treated at 500° C.for 1 hour while supplying a mixture of hydrogen and nitrogen having avolume ratio of 1:1. FIG. 8 is an SEM image of the henequen fibersheat-treated at 700° C. under the same conditions, FIG. 9 is an SEMimage of the henequen fibers heat-treated at 1000° C., and FIG. 10 is anSEM image of the henequen fibers heat-treated at 1500° C. As can be seenfrom FIGS. 7 to 10, the walls of the inner channels of the henequenfibers gradually become thinner as the heat treatment temperature isincreased. Also, it can be seen that the side surfaces of the fibersbecome rougher as the heat treatment temperature is increased. This maybe because, as described above, the impurities included in the henequenfibers are removed as the heat treatment temperature increases.

Test Example 4 Change in Characteristics of Henequen Fibers Depending onChemical Treatment Conditions

The henequen fibers electron beam- and heat-treated in Processes (1) and(2) of Example 1 were subjected to chemical treatment in Process (3). Inorder to compare formation of oxidizing groups (CO—, CH—, O—C═O, CO₂,CO₃, etc.) on the surface of the henequen fiber, X-ray photoelectronspectroscopy (XPS) was carried out. Results thereof are shown in FIG.11.

In FIG. 11, change in area ratio of 01s/C1s with increasing chemicaltreatment time is graphically represented in order to quantitativelycompare the amount of O1s bonding and C1 s bonding present in thecellulose catalyst support. As seen from FIG. 11, the quantity ofoxidizing groups increased almost linearly with the increasing treatmenttime. Thus, it can be confirmed that defects are effectively formed onthe surface of the henequen fibers through the acidic treatment.

Test Example 5 SEM Analysis Before and After Chemical Surface Treatmentof Cellulose Catalyst Support

The henequen fibers treated in Processes 1 and 2 of Example 1 wereeither left untreated (FIG. 12) or subjected to chemical treatment inProcess 3 (FIG. 13). Subsequently, after preparing Ni catalystssupported on cellulose catalyst supports by impregnation as in Example2, surface analysis was performed using SEM. Results thereof are shownin FIGS. 12 and 13. Chemical treatment conditions were as follows.First, the cellulose catalyst support was immersed in a 0.5M aqueoussulfuric acid solution and subjected to sweeping in 10 to 60 cycles from−0.15 to 1.3 V at a sweep rate of 50 mV/s. Then, the cellulose catalystsupport was immersed in a mixture of nitric acid (14M, 50 mL) andsulfuric acid (98%, 50 mL) and chemically treated at 60° C. for 10minutes under reflux. After sufficiently washing with distilled waterand filtering, the treated sample was dried at 110° C. for 12 hours.Thus, a cellulose catalyst support was prepared.

As can be seen from FIG. 12, the non-chemically treated cellulosecatalyst support showed agglomeration of Ni catalyst particles on thesupport surface, which resulted in a very low degree of dispersion.Also, since the active sites for catalytic reaction decrease as theparticles agglomerate, the activity of catalytic reaction wassignificantly decreased. In contrast, as can be seen in FIG. 13, thechemically treated sample showed uniformly supported Ni particles on thesupport surface. This is attributed to the fact that the functionalgroup such as CO— or CH— is introduced to the surface of the catalystsupport through chemical treatment and the metal catalyst particlesselectively bind to such defects, thereby allowing the metal catalystparticles to be supported on the catalyst support in a highly dispersedstate.

Test Example 6 Catalytic Reaction Test Using Catalyst Supported onCellulose Catalyst Support or Commercially Available Support

Pyrolysis of acetylene was carried out using the catalysts prepared inExample 1 and Comparative Example 1. Results thereof are compared inFIG. 14.

Pyrolysis of acetylene was performed from 250° C. while increasingtemperature in 50° C. intervals. The Ni catalyst supported on thecellulose catalyst support prepared in Example 1 showed initial reactionactivity at 250° C. of about 47%). Reaction activity decreased rapidlyto yield a conversion rate of about 14% after 1 hour. This is becausecokes produced in the early stages of pyrolysis of acetylene cover thecatalyst surface. The reaction activity gradually decreased to give aconversion rate of about 5% after 12 hours. When the reactiontemperature was increased to 300° C., the acetylene conversion rate wasalmost 100% initially but decreased to about 37% within 1 hour.Thereafter, the Ni catalyst supported on the cellulose catalyst supportprepared in Example 1 retained a reaction activity of about 23% evenafter 12 hours.

In contrast, when the Ni/Al₂O₃ catalyst prepared in Comparative Example1 using the commercially available catalyst support was used, thereaction hardly proceeded at 300° C. When the reaction temperature wasincreased to 350° C., a reaction activity was temporarily observedinitially, but it decreased to about 7% after 1 hour and a very lowconversion rate was obtained thereafter. Reactivity barely increasedeven when the reaction temperature was increased above 350° C.

Thus, it can be seen that the cellulose catalyst support facilitatescatalytic reactions such as pyrolysis of acetylene better than theexisting alumina support and that deactivation of the catalyst by cokegeneration resulting from prolonged reaction occurs slower than in thealumina support.

The present disclosure provides a method for pretreating aphysically/chemically durable catalyst support suitable for catalyticreactions from a fibrous biomaterial such as henequen fibers, which havea lot of micropores due to high cellulose content, by means of specificpretreatment. The resulting catalyst support has a large surface areaand uniform pore distribution and has metal catalyst nanoparticlessupported on the surface of the natural cellulose fibers wherefunctional groups are introduced in a highly dispersed state. Thus, thecatalyst support can be utilized for various catalytic reactions.

Although some embodiments have been described in the present disclosure,it should be understood that the embodiments are given by way ofillustration only and do not limit the scope of the present disclosure,and that various modifications and changes can be made by a personhaving ordinary knowledge in the art without departing from the spiritand scope of the present disclosure, which are limited only by theaccompanying claims and equivalents thereof.

What is claimed is:
 1. A method of preparing a catalyst having metalcatalyst nanoparticles supported on natural cellulose fibers,comprising: treating natural cellulose fibers with an electron beam;heat-treating the electron beam-treated natural cellulose fibers;chemically treating the heat-treated natural cellulose fibers with anacidic solution to introduce an oxidizing group to a surface of thenatural cellulose fibers to prepare a cellulose catalyst support; andsupporting metal catalyst nanoparticles on the cellulose catalystsupport by chemical vapor deposition or impregnation.
 2. The method ofclaim 1, wherein the electron beam treatment of the natural cellulosefibers comprises irradiating an electron beam of 10 to 500 kGy to thenatural cellulose fibers.
 3. The method of claim 1, wherein the heattreatment of the natural cellulose fibers comprises cutting the naturalcellulose fibers to a length of 1˜2 mm, with the natural cellulosefibers impregnated in liquid nitrogen, and heat-treating naturalcellulose fibers at 500˜1500° C. for 0.2 to 2 hours.
 4. The method ofclaim 1, wherein the chemical treatment of the natural cellulose fiberscomprises sweeping the heat-treated natural cellulose fibers in 10˜60cycles at −0.15˜1.3 V at a sweep rate of 50 mV/s, with the heat-treatednatural cellulose fibers immersed in a 0.1˜0.5M aqueous sulfuric acidsolution, followed by chemically treating the natural cellulose fibersfor 10˜20 minutes, with the natural cellulose fibers immersed in a 30%nitric acid solution (or 14N nitric acid solution) at 100˜150° C.
 5. Themethod of claim 1, wherein the chemical treatment of the naturalcellulose fibers comprises sweeping the heat-treated natural cellulosefibers in 10˜60 cycles at −0.15˜1.3V at a sweep rate of 50 mV/s, withthe heat-treated natural cellulose fibers immersed in 0.1˜0.5M aqueoussulfuric acid solution, followed by chemically treating the naturalcellulose fibers at 50˜70° C. for 5 minutes to 6 hours under reflux,with the natural cellulose fibers immersed in a mixture solution ofnitric acid and sulfuric acid.
 6. The method of claim 5, wherein themixture solution of nitric acid and sulfuric acid is a mixture solutionof nitric acid (14M, 50 mL) and sulfuric acid (98%, 50 mL) or a mixturesolution of 98% sulfuric acid and 70% nitric acid in a volume ratio of3:1.
 7. The method of claim 1, further comprising: washing and dryingthe chemically treated natural cellulose fibers to prepare the cellulosecatalyst support.
 8. The method of claim 1, wherein the oxidizing groupintroduced to the surface of the natural cellulose fibers comprises CO—,CH—, O—C═O, CO₂, or CO₃.
 9. The method of claim 1, wherein the metalcatalyst nanoparticles supported on the cellulose catalyst support bythe chemical deposition or impregnation comprise platinum particles, anda platinum precursor for supporting the platinum particles on thecellulose catalyst support is selected from the group consisting ofMeCpPtMe₃, Pt(Me)₃(Cp), Pt(Tfacac)₂, Pt(Me)(C0)(Cp), Pt(Me)₂(COD),[PtMe₃(acac)]₂, PtCl₂(CO)₂, Pt(PF₃)₄, Pt(acac)₂, and Pt(C₂H₄)₃.
 10. Themethod of claim 1, wherein the metal catalyst nanoparticles supported onthe cellulose catalyst support by the chemical deposition orimpregnation comprise nickel particles, and a nickel precursor forsupporting the nickel particles on the cellulose catalyst support isnickel nitrate (Ni(NO₃)₂) or nickel carbonyl (Ni(CO)₄).
 11. The methodof claim 1, wherein the metal catalyst nanoparticles supported on thecellulose catalyst support by the chemical deposition or impregnationcomprise cobalt particles, and a cobalt precursor for supporting thecobalt particles on the cellulose catalyst support is Co(CO)₃NO orCo(NO₃)₂.
 12. The method of claim 1, wherein the metal catalystnanoparticles supported on the cellulose catalyst support by thechemical deposition or impregnation comprise molybdenum particles, and amolybdenum precursor for supporting the molybdenum particles on thecellulose catalyst support is Mo(CO)₆.
 13. The method of claim 1,wherein the supporting the metal catalyst nanoparticles on the cellulosecatalyst support by the chemical vapor deposition comprises removingimpurities from within a quartz tube by placing the prepared cellulosecatalyst support at a center of the quartz tube and maintaining thequartz tube at a pressure of 6˜10 Torr at 110˜120° C. for 30˜120minutes; elevating an internal temperature of the quartz tube having thecellulose catalyst support therein to 80˜300° C.; and supplying agaseous metal precursor into the quartz tube under vacuum after a targetreaction temperature is reached, thereby allowing the metal catalystnanoparticles to be supported on the cellulose catalyst support.
 14. Themethod of claim 1, wherein the supporting the metal catalystnanoparticles on the cellulose catalyst support by the chemical vapordeposition comprises depositing the prepared cellulose catalyst supportin an aqueous solution of a metal precursor, ultrasonicating thecellulose catalyst support, drying the cellulose catalyst support, andburning the cellulose catalyst support in nitrogen atmosphere.